A Novel Waveguide to Enable MAS-DNP-NMR in Standard-bore High-field Magnets Abstract The critical importance of solid-state NMR (ssNMR) was recently demonstrated by, after nearly two decades of intense efforts, yielding the first atomic-resolution structures of the A?40 and A?42 amyloid fibrils that play a cru- cial role in Alzheimer?s Disease (AD). Key to that structure determination was a technique denoted as dynamic nuclear polarization (DNP) with magic angle spinning (MAS). While Cryo EM, scanning tunneling electron mi- croscopy (STEM) and other methods provided useful information, recent advances in MAS-NMR methods pro- vided essential restraints and additional crucial information, including sidechain dynamics important in protein functions and in understanding of myriad mechanisms of their action. Hence, developing transformational ad- vances for ssNMR is crucial for both structural biology and biomedical research in general, for progress in cur- ing Alzheimer?s Disease and cancer, and for providing regio-specific drug binding information enabling detailing of the mechanism of action for effective drugs. MAS-DNP systems thus far have all required specialized wide-bore (WB) magnets because known designs of waveguides compatible with THz transmission and the various relevant issues cannot be made small enough to work in probes for use in standard-bore (SB, also called narrow-bore, NB) magnets. The specialized WB magnets and the required corrugated THz waveguides constitute a large portion of the high system cost for MAS-DNP, which has put it out of reach to all but a few premiere laboratories. This proposed Phase I SBIR will show feasibility of a revolutionary broad-band multi-mode waveguide for use in the 85-1000 GHz range (as needed for NMR at 3-35 T) that can easily be manufactured at diameters small enough to make MAS-DNP probes practical in existing NB high-field magnets. Attenuation is predicted to be two orders of magnitude be- low that of fundamental-mode waveguides at 400 GHz and even lower than that of the very expensive corru- gated over-moded waveguides for a wide range of applications. It is expected that this advance, in combination with several other technological advances being pursued in other projects, will eventually enable DNP to be added to existing ssNMR high-field systems without the re- quirement of either a specialized magnet or a gyrotron.